An uplink of LTE-Advanced, which is the developed 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), involves two techniques under study, i.e., non-contiguous band transmission and MU-MIMO (Multiple User-Multiple Input Multiple Output), in order to enhance scheduling gain by flexible frequency resource allocation.
Firstly, the non-contiguous band transmission will be explained. LTE only has used contiguous band transmission allocating a data signal of each terminal to contiguous frequency bands in order to reduce the CM (Cubic Metric) and the PAPR (Peak to Average Power Ratio). Meanwhile, the uplink of LTE-Advanced has a schedule to use the non-contiguous band transmission in addition to the contiguous band transmission in order to improve cell throughput performance (see, Non-Patent Literature 1).
The non-contiguous hand transmission is a technique to allocate data signals and reference signals to non-contiguous frequency bands widely distributed to a hand. As illustrated in FIG. 1, the non-contiguous band transmission can allocate the data signals and the reference signals to distributed frequency bands. The non-contiguous band transmission thus has enhanced flexibility of the allocation of the data signals and reference signals of terminals to the frequency bands and can acquire larger frequency scheduling effect compared to the contiguous band transmission.
Secondly, MU-MIMO will be explained. MU-MIMO is a technique, which a plurality of terminals perform MIMO communication with a base station, can enhance the frequency use efficiency and thus throughput performance of the system. In MU-MIMO, to demultiplex transmission data of each terminal at a reception side, DM-RSs (DeModulation-Reference Signals) between the terminals need to be orthogonalized. The MIMO can perform space division multiplexing transmission of different signal sequences in the same frequency between a plurality of antennas provided at a transmission station and a plurality of antennas at a reception station.
A conventional technique in which the base station notifies the terminals of non-contiguous hand allocation resource information involves transmission of a plurality of RIVs (Resource Indication Values) to one terminal to notify the terminals of the non-contiguous band allocation (see Non-Patent Literatures 2 and 3).
RIVs forming a tree structure as illustrated in FIG. 2 represent allocation resource information. FIG. 2 illustrates the RIVs tree structure indicating contiguous band allocation in the range of RB#0 to RB#5. For example, when a base station indicates RIV=6, the allocation resource information to terminals includes RB#0 and RB#1 located in the bottom of the tree. When the base station indicates RIV=14, the allocation resource information to the terminals includes RB#2 to RB#4 located in the bottom of the tree. RB#0 to RB#5 located in the bottom of the tree correspond to RIVs=0 to 5, respectively.
When RIVs=0 to 5 in the bottom of the tree are considered as the first stage, RIVs=6 to 10 form the second stage, RIVs=12 to 15 form the third stage, RIVs=18 to 20 form the fourth stage, RIVs=17 and 16 form the fifth stage, and RIV=11 form the sixth stage. 21 patterns of contiguous bands can be indicated from RB#0 to RB#5 located in the bottom of the tree using these RIVs forming the first stage to the sixth stage.
For example, reporting two RIVs can instruct the terminal to perform non-contiguous band allocation of up to two clusters (a set of contiguous bands), as illustrated in FIG. 3. As illustrated in FIG. 4, a bandwidth represented by each RIV may be a part of a system bandwidth, making it possible to reduce the number of signaling bits.
In MU-MIMO, to demultiplex transmission data of each terminal at a reception side, DM-RSs (DeModulation-Reference Signals) of the terminals need to be orthogonalized. FIG. 5 shows a DM-RS transmitting technique for non-contiguous band allocation. This technique generates a ZC (Zadoff-Chu) sequence on a cluster basis, and orthogonalizes DM-RSs of different terminals by the CS-ZC sequences in which different amounts of cyclic shift (CS) are set between the terminals to be MU-MIMO multiplexed. Here, ZC sequence is a code segue